A computer network is a collection of interconnected computing devices that can exchange data and share resources. Example network devices include switches or other layer two devices that operate within the second layer (L2) of the Open Systems Interconnection (OSI) reference model, i.e., the data link layer, and routers or other layer three (L3) devices that operate within the third layer of the OSI reference model, i.e., the network layer. Network devices within computer networks often include a control unit that provides control plane functionality for the network device and forwarding components for routing or switching data units.
An Ethernet Virtual Private Network (EVPN) may be used to extend two or more remote layer two (L2) customer networks through an intermediate layer three (L3) network (usually referred to as a provider network), in a transparent manner, i.e., as if the intermediate L3 network does not exist. In particular, the EVPN transports L2 communications, such as Ethernet packets or “frames,” between customer networks via traffic engineered label switched paths (LSP) through the intermediate network in accordance with one or more multiprotocol label switching (MPLS) protocols. In a typical configuration, provider edge (PE) devices (e.g., routers and/or switches) coupled to the customer edge (CE) network devices of the customer networks define label switched paths (LSPs) within the provider network to carry encapsulated L2 communications as if these customer networks were directly attached to the same local area network (LAN). In some configurations, the PE devices may also be connected by an IP infrastructure in which case IP/GRE tunneling or other IP tunneling can be used between the network devices.
In an EVPN, L2 address learning (also referred to as “MAC learning”) on a core-facing interface of a PE device occurs in the control plane rather than in the data plane (as happens with traditional bridging) using a routing protocol. For example, in EVPNs, a PE device typically uses the Border Gateway Protocol (BGP) (i.e., an L3 routing protocol) to advertise to other provider edge network devices the MAC addresses the PE device has learned from the local consumer edge network devices to which the PE device is connected. As one example, a PE device may use a BGP route advertisement message to announce reachability information for the EVPN, where the BGP route advertisement specifies one or more MAC addresses learned by the PE device instead of L3 routing information. Additional example information with respect to EVPN is described in “BGP MPLS-Based Ethernet VPN,” Request for Comments (RFC) 7432, Internet Engineering Task Force (IETF), February, 2015, the entire contents of which are incorporated herein by reference.
A Provider Backbone Bridged Ethernet Virtual Private Network (PBB-EVPN) combines EVPN services with MAC-in-MAC encapsulation when transporting L2 communications. That is, a customer frame transported through the PBB-EVPN has MAC-in-MAC encapsulation in which customer MAC (C-MAC) addresses within the header are encapsulated within backbone MAC (B-MAC) addresses, thereby maintaining separation between the provider L2 domain and the customer L2 domain. In PBB-EVPN, PEs distribute reachability information for B-MAC addresses associated with local Ethernet segments using EVPN route advertisements, and remote PEs receive encapsulated customer frames and learn, via the data plane, the C-MAC addresses in association with the remote B-MACs for traffic. Additional example information with respect to PBB-EVPN is described in “Provider Backbone Bridging Combined with Ethernet VPN (PBB-EVPN),” Request for Comments (RFC) 7623, Internet Engineering Task Force (IETF), September, 2015, the entire contents of which are incorporated herein by reference.